1. Field of the Invention
The present invention relates to a numerical controller that enables a method for alarm notification to be changed depending on the type of an abnormality at the time of access to a device or a memory.
2. Description of the Related Art
A numerical controller used to control a machine tool includes a central processing unit (CPU) for operations, a memory in which an OS and the like are stored, a memory control circuit that controls the memory, an axis control circuit that controls axes, and a display control circuit for display.
A configuration of a conventional numerical controller will be described with reference to FIG. 5.
A numerical controller 10 is internally provided with a CPU 20, a bus control circuit 30 that controls a bus, an axis control circuit 40 that controls an axis, a display control circuit 50 that controls a display apparatus, a memory 70, and a memory control circuit 60 used to control the memory 70. Data for data abnormality detection 80 (parity data or ECC) is stored in the memory 70. Furthermore, the axis control circuit 40, the display control circuit 50, the memory control circuit 60, and the memory 70 are connected together via a bus 90. The bus 90 is controlled by the bus control circuit 30. Moreover, the CPU 20 and the bus 90 are connected together via a bus connection circuit (not depicted in the drawings).
Exchange of signals during an axis control process in the numerical controller 10 in FIG. 5 will be described using FIG. 6.
The CPU 20 exchanges signals with the bus control circuit 30 to acquire data in the memory 70 from the bus control circuit 30 through the memory control circuit 60 to control axes (not depicted in the drawings) through the axis control circuit 40.
Exchange of signals in the numerical controller in FIG. 5 during a process of controlling a display apparatus will be described using FIG. 7.
The CPU 20 exchanges signals with the bus control circuit 30 to acquire data in the memory 70 from the bus control circuit 30 through the memory control circuit 60 to control the display apparatus (not depicted in the drawings) through the display control circuit 50.
In this regard, the data for data abnormality detection 80 in the memory 70 is monitored by the memory control circuit 60. If the memory control circuit 60 detects an abnormality in the data in the memory 70, the memory control circuit 60 delivers an alarm to the CPU 20. FIG. 8 depicts processing executed at the time of a data abnormality in the memory 70. As is the case with a state depicted in FIG. 7, when data is externally disturbed during a display control process, the memory control circuit 60 detects an abnormality in the data and delivers an alarm to the CPU 20. Upon receiving the alarm, the CPU 20 stops processing.
Furthermore, like the memory 70, the bus 90, which allows for access to the memory or device, is provided with data for data abnormality detection. Each control circuit monitors received data for abnormality, and if an abnormality is detected, the control circuit delivers an alarm to the CPU 20. Upon receiving the alarm, the CPU 20 stops processing.
Moreover, the bus control circuit 30 has a function to monitor the cycle time of the bus 90, and also delivers an alarm to the CPU 20 if an abnormality is detected such as no response to access to any of the control circuits. FIG. 9 depicts such a state. When the cycle of the bus 90 is externally disturbed during a process of controlling the display apparatus, the bus control circuit 30 detects a cycle abnormality and delivers an alarm to the CPU 20. Upon receiving the alarm, the CPU 20 stops the processing.
Furthermore, each of the control circuits has a function to check data from the bus 90, and upon detecting an abnormality in the data received from the bus 90, delivers an alarm to the CPU 20. FIG. 10 depicts such a state. When the data from the bus 90 is externally disturbed during a process of controlling the display apparatus, the display control circuit 50 detects an abnormality in the data and delivers an alarm to the CPU 20. Upon receiving the alarm, the CPU 20 stops processing.
As described above, a conventional machine tool stops processing when any of the control circuits delivers an alarm to the CPU 20. This is carried out for safety concern because, when the axes perform an unexpected operation due to malfunction, the machine may be damaged or an accident may occur.
Japanese Patent Application Laid-Open No. 2009-104246 discloses a technique in which an operating status is determined in a CPU module for PLC determines, and when an abnormal state is detected, the CPU module for PLC is shut down, and when subsequently determined that the abnormality is temporary, the CPU module for PLC is restarted using restart means.
In conventional techniques, whatever abnormality occurs, any of the control circuits delivers an alarm to the CPU 20 to cause the CPU 20 to stop processing. In this regard, in a machine tool controlled by the numerical controller, when processing is stopped before completion, a time loss occurs as a result of restarting and the like. Furthermore, when processing is stopped during machining, a machined surface may be affected by the stoppage, leading to a loss in material. In particular, in machining of molds or the like, machining of one mold may need several hours. Thus, when the machining is stopped before completion, a significant temporal loss may occur.
Even in the technique disclosed in Japanese Patent Application Laid-Open No. 2009-104246, the CPU module for PLC is restarted when the abnormality is determined to be temporary, but the processing is temporarily stopped when the abnormality occurs. Thus, a loss in time or material may result from the stoppage of the processing as is the case with the conventional techniques.